/*
* Copyright 2002-2010 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.expression.spel.ast;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import org.springframework.core.MethodParameter;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.expression.EvaluationException;
import org.springframework.expression.TypeConverter;
import org.springframework.expression.TypedValue;
import org.springframework.expression.spel.ExpressionState;
import org.springframework.expression.spel.SpelEvaluationException;
import org.springframework.expression.spel.SpelMessage;
import org.springframework.expression.spel.support.ReflectionHelper;
import org.springframework.util.ReflectionUtils;
/**
* A function reference is of the form "#someFunction(a,b,c)". Functions may be defined in the context prior to the
* expression being evaluated or within the expression itself using a lambda function definition. For example: Lambda
* function definition in an expression: "(#max = {|x,y|$x>$y?$x:$y};max(2,3))" Calling context defined function:
* "#isEven(37)". Functions may also be static java methods, registered in the context prior to invocation of the
* expression.
*
* <p>Functions are very simplistic, the arguments are not part of the definition (right now),
* so the names must be unique.
*
* @author Andy Clement
* @since 3.0
*/
public class FunctionReference extends SpelNodeImpl {
private final String name;
public FunctionReference(String functionName, int pos, SpelNodeImpl... arguments) {
super(pos,arguments);
name = functionName;
}
@Override
public TypedValue getValueInternal(ExpressionState state) throws EvaluationException {
TypedValue o = state.lookupVariable(name);
if (o == null) {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.FUNCTION_NOT_DEFINED, name);
}
// Two possibilities: a lambda function or a Java static method registered as a function
if (!(o.getValue() instanceof Method)) {
throw new SpelEvaluationException(SpelMessage.FUNCTION_REFERENCE_CANNOT_BE_INVOKED, name, o.getClass());
}
try {
return executeFunctionJLRMethod(state, (Method) o.getValue());
}
catch (SpelEvaluationException se) {
se.setPosition(getStartPosition());
throw se;
}
}
/**
* Execute a function represented as a java.lang.reflect.Method.
*
* @param state the expression evaluation state
* @param the java method to invoke
* @return the return value of the invoked Java method
* @throws EvaluationException if there is any problem invoking the method
*/
private TypedValue executeFunctionJLRMethod(ExpressionState state, Method method) throws EvaluationException {
Object[] functionArgs = getArguments(state);
if (!method.isVarArgs() && method.getParameterTypes().length != functionArgs.length) {
throw new SpelEvaluationException(SpelMessage.INCORRECT_NUMBER_OF_ARGUMENTS_TO_FUNCTION,
functionArgs.length, method.getParameterTypes().length);
}
// Only static methods can be called in this way
if (!Modifier.isStatic(method.getModifiers())) {
throw new SpelEvaluationException(getStartPosition(), SpelMessage.FUNCTION_MUST_BE_STATIC, method
.getDeclaringClass().getName()
+ "." + method.getName(), name);
}
// Convert arguments if necessary and remap them for varargs if required
if (functionArgs != null) {
TypeConverter converter = state.getEvaluationContext().getTypeConverter();
ReflectionHelper.convertAllArguments(converter, functionArgs, method);
}
if (method.isVarArgs()) {
functionArgs = ReflectionHelper.setupArgumentsForVarargsInvocation(method.getParameterTypes(), functionArgs);
}
try {
ReflectionUtils.makeAccessible(method);
Object result = method.invoke(method.getClass(), functionArgs);
return new TypedValue(result, new TypeDescriptor(new MethodParameter(method,-1)));
}
catch (Exception ex) {
throw new SpelEvaluationException(getStartPosition(), ex, SpelMessage.EXCEPTION_DURING_FUNCTION_CALL,
this.name, ex.getMessage());
}
}
@Override
public String toStringAST() {
StringBuilder sb = new StringBuilder("#").append(name);
sb.append("(");
for (int i = 0; i < getChildCount(); i++) {
if (i > 0)
sb.append(",");
sb.append(getChild(i).toStringAST());
}
sb.append(")");
return sb.toString();
}
// to 'assign' to a function don't use the () suffix and so it is just a variable reference
/**
* Compute the arguments to the function, they are the children of this expression node.
* @return an array of argument values for the function call
*/
private Object[] getArguments(ExpressionState state) throws EvaluationException {
// Compute arguments to the function
Object[] arguments = new Object[getChildCount()];
for (int i = 0; i < arguments.length; i++) {
arguments[i] = children[i].getValueInternal(state).getValue();
}
return arguments;
}
}
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